U.S. patent application number 11/703895 was filed with the patent office on 2007-06-21 for printable snap-breakable sheet.
Invention is credited to Chia-Hsi Chu, Ramin Heydarpour, Karl Lengfeller, Ali R. Mehrabi, Ronald Ugolick, Martin Utz, Sriram Venkatasanthanam, Michael Wilkes.
Application Number | 20070141292 11/703895 |
Document ID | / |
Family ID | 7696826 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070141292 |
Kind Code |
A1 |
Utz; Martin ; et
al. |
June 21, 2007 |
Printable snap-breakable sheet
Abstract
A card sheet including a top material having punched lines, the
front side of the top material being printable. A carrier material
of at least one polymer layer is directly applied as by extruding
to the back side of the top material. The polymer has a
stress-at-break in the range of 10 to 30 MPa and an elongation at
break in the range of 10 to 120%. From the card sheet individual
cards may be broken out to form high quality calling (business)
cards, photograph cards, post cards or the like.
Inventors: |
Utz; Martin; (Munchen,
DE) ; Lengfeller; Karl;
(Grosskarolinenfeld/Tattenhause, DE) ; Wilkes;
Michael; (Arzbach, DE) ; Venkatasanthanam;
Sriram; (Chino Hills, CA) ; Heydarpour; Ramin;
(Beverly Hills, CA) ; Chu; Chia-Hsi; (Arcadia,
CA) ; Ugolick; Ronald; (San Dimas, CA) ;
Mehrabi; Ali R.; (Los Angeles, CA) |
Correspondence
Address: |
JEFFER, MANGELS, BUTLER & MARMARO, LLP
1900 AVENUE OF THE STARS, 7TH FLOOR
LOS ANGELES
CA
90067
US
|
Family ID: |
7696826 |
Appl. No.: |
11/703895 |
Filed: |
February 8, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11001560 |
Nov 30, 2004 |
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11703895 |
Feb 8, 2007 |
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10233283 |
Aug 28, 2002 |
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11001560 |
Nov 30, 2004 |
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Current U.S.
Class: |
428/43 ;
428/167 |
Current CPC
Class: |
B32B 29/00 20130101;
B26D 3/085 20130101; C08K 5/1575 20130101; Y10T 428/24612 20150115;
B32B 2307/538 20130101; B32B 38/0004 20130101; B32B 2317/12
20130101; B32B 27/32 20130101; B42D 15/02 20130101; Y10T 428/24314
20150115; B32B 37/153 20130101; B32B 2309/105 20130101; B32B 38/145
20130101; Y10T 156/1052 20150115; B32B 27/10 20130101; B32B 3/00
20130101; C08K 3/013 20180101; B26F 1/40 20130101; B32B 3/266
20130101; B32B 37/08 20130101; B42D 5/027 20130101; Y10T 428/2457
20150115; C08K 5/0083 20130101; B32B 2307/718 20130101; B32B
2309/10 20130101; Y10T 428/15 20150115; B32B 2038/042 20130101;
B32B 2038/045 20130101; B32B 2307/75 20130101; B32B 2425/00
20130101 |
Class at
Publication: |
428/043 ;
428/167 |
International
Class: |
G09F 3/00 20060101
G09F003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2001 |
DE |
101.42.043.9 |
Claims
1-151. (canceled)
152. A printable sheet comprising: a polymer film sheet; cut lines
penetrating a partial thickness of the printable sheet and defining
perimeter edges of subdivided sheets; the printable sheet having a
printable surface; and the polymer film sheet having
elongation-at-break and stress-at-break properties such that after
the printable sheet has been passed through a printer or copier and
a printing operation conducted on the printable surface, the
printable sheet snap-breaks along the die cut lines when the
printable sheet is folded on the lines to form individual printed
subdivided sheets.
153. The printable sheet of claim 152 wherein the cut lines
penetrate a partial thickness of the polymer film sheet.
154. The printable sheet of claim 152 wherein the polymer film
sheet is a polyolefin film sheet.
155. The printable sheet of claim 152 wherein the polymer of the
polymer film sheet is selected from the group of polymethylpentene,
polyolefins, polyesters, polymethyl methacrylate, polystyrene, and
compatible mixtures thereof.
156. The printable sheet of claim 155 wherein the polyolefins are
selected from the group of polypropylene, polyethylenes, and
copolymers of propylene and ethylene.
157. The printable sheet of claim 152 wherein the printable sheet
defines a card sheet, and the printed subdivided sheets define
printed cards.
158. The printable sheet of claim 152 wherein the printable surface
is photoreceptive and the printed subdivided sheets are photo
cards.
159. The printable sheet of claim 152 wherein the printed
subdivided sheets are business cards.
160. The printable sheet of claim 152 wherein the printable sheet
is a single layer sheet.
161. The printable sheet of claim 152 wherein the printable sheet
is a multi-layer sheet.
162. The printable sheet of claim 152 wherein the polymer film
sheet includes a polymer and a filler.
163. The printable sheet of claim 152 wherein the polymer film
sheet includes a polymer and a nucleating agent.
164. The printable sheet of claim 152 wherein the printable surface
is a printable topcoat.
165. The printable sheet of claim 152 wherein the printable surface
is a top surface of the polymer film sheet and an opposite bottom
surface of the polymer film sheet is a printable surface.
166. The printable sheet of claim 152 wherein the printable surface
is capable of receiving an image from an inkjet or laser
printer.
167. The printable sheet of claim 152 wherein the printable sheet
snap-breaks after only a single folding action on one of the cut
lines.
168. The printable sheet of claim 167 wherein the single folding
action is towards the top surface.
169. The printable sheet of claim 152 wherein the polymer film
sheet is 8 1/2 .times.11 inches, 81/2.times.14 inches or A4
size.
170. The printable sheet of claim 152 wherein the polymer film
sheet comprises polymethylpentene.
171. The printable sheet of claim 152 wherein the polymer film
sheet includes a crystalline polymer.
172. The printable sheet of claim 152 wherein the polymer film
sheet includes a semicrystalline polymer.
173. The printable sheet of claim 152 wherein the polymer film
sheet has the printable surface.
174. The printable sheet of claim 152 wherein the printable surface
is a top surface of the polymer film sheet and a bottom surface of
the printable sheet is also a printable surface.
175. The printable sheet of claim 152 wherein the cut lines are die
cut lines.
176. The printable sheet of claim 152 wherein the polymer film
sheet is a polyolefin selected from the group of polypropylene,
polyethylenes, and copolymers of propylene and ethylene.
177. The printable sheet of claim 152 wherein the cut lines form a
grid of cut lines.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to sheets of calling or
business cards, photograph cards, post cards and the like, methods
of making them and methods of using them.
[0002] The design of calling or business cards by simply printing
them with commercially available laser or inkjet printers is of
interest. Small size printable media, such as calling or business
cards, cannot be individually printed with conventional laser or
inkjet printers due to their small format. For this reason, for
printing calling cards by means of a laser printer or an inkjet
printer, card sheets are usually initially used, from which the
calling cards are separated after having been printed, leaving a
residual "matrix" of the card sheet. In these card, sheets a
supporting structure is provided for the cards and a wide variety
of embodiments are known for such card sheets and carriers.
[0003] ln a first class of card sheets, the matrix of the card
sheet, or a portion of that matrix, itself acts as the carrier for
the cards. Thus, there are calling card sheets in which the
material is microperforated and the card is broken out along the
microperforations to separate the cards from the matrix. The cards
to be separated and having a microperforation are connected to the
card sheet by material bridges. When the cards are separated from
the card sheet, these bridges partially remain at the edges of the
cards. These separation residues are unsightly and not desired
especially for high-quality products, such as calling cards.
[0004] ln one variation of this first class of card, sheet product,
instead of microperforations, the card sheet includes die cut lines
penetrating much but not all of the card sheets ("substantially
cut" lines), and cards are separated from the surrounding matrix by
severing the uncut portions of the substantially cut lines. Another
variation uses a multi-layer structure for the card sheet, wherein
one of the layers acts as the carrier material. In these
variations, the same problem mentioned above may occur, i.e.,
unsightly residual material after separation of cards. Patent
publications illustrating this first class of card products
include: U.S. Pat. No. 5,853,837 (Popat, commonly assigned
herewith; substantially cut lines); see also U.S. patent
application Ser. No. 2001/0036525 A1 (Yokokawa; multilayer card
structure). (The entire contents of all patents and other
publications mentioned anywhere in this disclosure are hereby
incorporated herein by reference.)
[0005] In a second class of card product designs, the cards are
completely cut from the surrounding matrix by cut punching, and one
or more additional structures are used as a carrier for the cut
cards. The structure of such cut-punched calling card sheets
results from a printable top material and a carrier material
applied to one side of the top material, the carrier material being
bonded to the cards and to the matrix to support the cards within
the matrix. One example of this second class of card products uses
relatively narrow carrier strips or tapes, which are applied to the
punched lines along the short side of the (A4) sheet, from which
the printed card may be drawn off. The adhesive remains on the
self-sealing tapes when the card is drawn off. A disadvantage of
this construction is that the top material/carrier connection is
relatively unstable, which impairs the feeding and transportation
behavior in the printer. In addition, there is the danger that tape
fibers are torn-off by the action of removing the cards from the
adhesive tape. This embodiment is shown in U.S. Pat. No. 5,702,789
(Fernandez-Kirchberger et al.).
[0006] Other versions of this second class of card sheet products
use a "liner" sheet as the carrier, wherein the liner may be a full
sheet corresponding to the top sheet, or may have sections removed
from a full sheet. In so-called "dry-peel" constructions, the bond
between the liner and the top sheet is created using an extruded
polymer with a debondable interface to the top sheet or to the
liner sheet. In removable or ultra-removable adhesive
constructions, the bond is created using a removable adhesive
between the top sheet and the liner sheet. When the cards are drawn
off from the carrier, the adhesive remains on the reverse side of
the card, which leads to a tangible and visible change as well as
to a limited writeability of the reverse side of the card, which is
judged to be of inferior quality.
[0007] Alternatively, a method is known in which a calling card
sheet, which initially was coated on the reverse side with a
silicon layer, is fastened onto a carrier material with an
adhesive. The calling card sheet is cut-punched and, after having
been printed, the individual calling cards can be drawn-off from
the carrier material. Due to the silicon layer, the adhesive
remaining on the reverse side of the calling card can be avoided.
These calling cards, however, have an altered smooth reverse side,
which is undesirable. In addition, such a reverse side has the
disadvantage that its writeability is inferior. A further
disadvantage is that the card is easily bent when it is drawn off
from the adhesive carrier. Examples of this second class of card
sheet products and dry peel laminates are shown in U.S. Pat. No.
4,863,772 (Cross, commonly assigned herewith), and PCT Publication
Nos. WO 00/16978 and WO 00/46316 (both of Avery Dennison
Corporation).
SUMMARY OF THE INVENTION
[0008] Pursuant to a preferred embodiment, the present invention is
directed to card sheets, from which cards can be separated by
simply breaking them out from the sheet, with the cards having
smooth edges. The front and the reverse sides of the card sheet
preferably feel the same to the touch. More particularly, the card
sheet comprises a top material having punched or die cut lines, the
front of which is printable and on the reverse of which a carrier
material of at least one polymer layer is directly applied. The
polymer can comprise a stress-at-break in the range of ten to
thirty MPa and an elongation at break in the range of one to 300%
(or ten to 300% or ten to 120%).
[0009] The (polymer) layer extruded on the top material cardstock
can be. poly-4-methyl-1-pentene (polymethyl pentene or TPX).
However, higher melt flow polypropylene (PP) resins may provide
better bonding. Examples of alternative polymers are thirty-five
melt flow index (MFI) nucleated PP (Basell PD702N) and the same
material with no nucleator (Basell PD702). These two materials can
be compounded with a filler. A further alternative is thirty-four
MFI, extrusion coating grade PP resin (Basell PDC-1292). Usable
extruded polymers are: polypropylene; nucleated polypropylene;
polypropylene followed by subsequent heat aging (120.degree.
F.-200.degree. F. for two days); filled polypropylene (filled with
thirty parts per hundred of three micron calcium carbonate); and
polymethylmethacrylate (acrylic).
[0010] One alternative way of applying the carrier material to the
top material is to apply a pre-polymer to the back side top
material and then cure it with UV light to form the film.
Subsequently, the top material is die cut to outline the card
perimeters. Although die cutting is the preferred way to form the
weakened perimeter lines, other less preferable techniques such as
microperfing can be used.
[0011] Instead of having a paper top layer on top of one or more
film layers, the card sheet construction can be a polymeric film
construction. The surface(s) of the construction which define the
printable card surface(s) should be printable. This can be done by
using a film itself which is printable or by applying a printable
coating. For example, the film can be formed from a melt
processable blend of a water-soluble polymer and a substantially
water-insoluble polymer to provide an inherently print receptive
surface without further surface treatment as described in WO
01/76885.
[0012] The film-only construction can comprise a photosheet with
die cuts on one side (or through both sides) to form the perimeters
of the photo cards. The die cuts can penetrate between fifty and
98% of the thickness of the photosheet construction.
[0013] A preferred embodiment directly applies, as by extrusion,
the (polymer) carrier material on the top material (cardsheet).
This has a number of advantages over using adhesive to secure the
two layers together. Adhesive makes the construction less stiff,
and high stiffness is a highly desirable feature for business
cards. The adhesive coating is visible on the backside of the card
in areas where the adhesive does not wet out very well and there is
imperfect contact between the two non-adhesive layers having
different shades. This visibility can make the business cards,
which are high quality products, unacceptable.
[0014] The thickness of the carrier of the present invention and
its unique mechanical properties allow for die cutting only on the
top. Advantageously, this allows for a clean snap-break with only a
single folding action. In other words, the user advantageously does
not have to fold it back and forth to break it. "Snap break" herein
means that the carrier yields during bending to a point, less than
fully folded, where the carrier suddenly breaks. The single folding
action, for example, can be forward between forty-five and one
hundred and sixty-five degrees.
[0015] One embodiment of the invention is TPX that is extruded,
treated on both sides with a printable topcoat (a primer might be
needed), die cut partially through, then sheeted. Depending on the
grade of polymer, one would choose material that has low elongation
at break and high tensile strength, but not so high in tensile
strength that it breaks when partially diecut. The stiffness must
also be correct (somewhat adjustable by caliper) so that it has
desired properties. The breaking apart of the cards may occur in
either folding direction depending on the sheet construction. The
choice of material can be such that folding toward the face would
create sufficient leverage along the cut that the door analogy
described later in the disclosure would be applicable. A less
preferable alternative might need to be folded away from the die
cut to "weaken" the "hinge", which then breaks when subsequently
folded toward the face.
[0016] Other possible resin materials include some of the PE's ,
such as HDPE, PP, PET (there are several varieties of PET) and
polystyrene. The resins might also contain. various fillers such as
clay, TiO.sub.2 and/or nucleating agents to further modify the
mechanical properties. The caliper of the sheet construction
depends on the desired application, but for "cards", anywhere from
about seven to twelve or fifteen mils might be reasonable.
[0017] Other inventions herein are a method for analysis of optical
roughness of a fracture interface and objects or articles having at
least one edge whose roughness is defined by that method.
[0018] Other advantages of the present invention will become more
apparent to those persons having ordinary skill in the art to which
the present invention pertains from the foregoing description taken
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a top plan view of a card sheet of the present
invention;
[0020] FIG. 2 is a perspective view of a printer (or copier)
showing a stack of card sheets of FIG. 1 being inserted therein and
printed;
[0021] FIG. 3 is an enlarged cross-sectional view of the card sheet
of FIG. 1 taken on line 3-3;
[0022] FIG. 4 is a schematic showing a process for manufacturing
the card sheet of FIG. 1;
[0023] FIG. 5 is a view similar to FIG. 3 showing a first
alternative card sheet of the invention;
[0024] FIG. 6 shows a second alternative;
[0025] FIGS. 7a-7c show the snap-break mechanism steps of a card
sheet of the invention;
[0026] FIG. 8 shows a third alternative;
[0027] FIG. 9 shows a fourth alternative;
[0028] FIG. 10 is a digital view of a fracture interface of an.
embodiment of this invention;
[0029] FIGS. 11 (a), (b), and (c). show original, binary and
de-speckled images, respectively, using an enhancement process from
the digital view of FIG. 10;
[0030] FIG. 12 is an eroded image;
[0031] FIG. 13 shows a final fracture interface image
extraction;
[0032] FIG. 14 are captured images of a fracture interface; and
[0033] FIG. 15 shows an interface contour extracted for a product
of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0034] A card sheet of the present invention is shown generally at
100 in FIG. 1. A stack of the card sheets 100 can be placed in the
input tray of a printer (or copier) shown generically at 104 in
FIG. 2. The desired indicia 110 can be printed on the cards 120 of
the card sheet by the printer (or copier) 104.
[0035] The card sheet 100 according to one embodiment of the
invention comprises a top material 130 and a carrier material 134
directly applied to a bottom surface of the top material, as shown
in the cross-sectional view of FIG. 3. Weakened separation lines
140 (such as die cut lines) through the top material 130 form the
perimeters of the cards 120.
[0036] A "printable top material" means materials that can be
printed with an inkjet printer and/or a laser printer 104 or other
commercial printing methods such as offset printing, and/or by
writing instruments. (Writing instruments can include pens, pencils
or the like.) As top material 130, generally any card materials may
be used which can be printed with an inkjet printer and/or a laser
printer 104. Such card materials can, for example, also be coated
or uncoated, dull or glossy, marmorated or obliquely transparent
or-they can have a linen or other topographic structure. When the
cards 120 are to be calling or business cards, a card material
having a grammage of one hundred and sixty to two hundred and fifty
g/m.sup.2 is preferred. Examples of preferred card materials
include matte coated paper available from Felix Schoeller Specialty
Papers (Osnabruck, Germany) and photoreceptive papers from Kanzaki
Specialty Papers (Springfield, Mass.); as well as laser papers
available from Kohler (Germany), Neusiedler Group (Austria), and
Monadnock Paper Mills (New Hampshire). The papers, when used in
conjunction with the carrier, have a caliper suitable for the
desired use, such as business cards or photo cards.
[0037] ln order to separate individual cards 120 from the card
sheet 100, the top material 130 preferably has punched or die cut
lines 140. On the other hand, the polymer-layer 134 is preferably
not punched, though punching or die cutting (140) which dents but
does not pierce or which penetrates only a slight distance can be
used for certain applications. To provide a carrier material for
cards punched within the card sheet 100, the polymer layer 134
preferably is applied directly onto the reverse side of the top
material 120 such as by extrusion. If the top material 130 has a
grammage of one hundred and sixty to two hundred and fifty
g/m.sup.2, the polymer layer 134 applied thereto preferably has a
grammage of fifteen to forty-five g/m.sup.2.
[0038] The separation of individual cards 120 from the card sheet
100 of the invention is carried out by bending along the punched
lines 140 in the direction to the top material, whereby the polymer
layer 134 snap-breaks cleanly along the punched lines. For this
purpose, the elongation at break of the polymer layer 134 should be
exceeded; that is, the elastic and plastic deformation of the
polymer layer 134 should be as small as possible. In addition, the
polymer layer must have a small resistance to further tearing. In
other words, it should be brittle, so that when one side of the
polymer layer is subjected to tension exceeding its elongation at
break, the break will continue to the side that is not bent. It is
thus a preferred feature of the invention that the polymer of which
the polymer layer 134 applied to the reverse side of the top
material 130 consists, has a stress-at-break in the range of ten to
thirty MPa, preferably sixteen MPa, and an elongation at break in
the range of ten to 120%, preferably twenty to 50%. The data on
stress-at-break and elongation at break refer to EN-ISO
527-3/2/500. The data on the bending stress. refer to EN-ISO
178.
[0039] The elongation at break of the polymer layer 134 further
depends on the thickness of the top material 130. The thicker the
top material 130 the greater the elongation of the polymer layer
134 is and the sooner the stress-at-break of the polymer layer 134
is attained. For this reason, the top material 130 preferably has a
grammage greater than one hundred and fifty g/m.sup.2, in
particular in the range of one hundred and sixty to two hundred and
fifty g/m.sup.2.
[0040] The polymer of the carrier material 134 applied to the
reverse or back side of the card sheet preferably has a bending
stress in the range of 600 to 1200 MPa, and a bending stress of 600
to 900 MPa is preferred. In a preferred embodiment, the polymer has
an elongation at maximum tensile strength from two to ten
percent.
[0041] A simplified schematic view of a manufacturing process for a
preferred card sheet 100 is illustrated in FIG. 4 generally at 200.
Referring thereto, the cardstock material 210 is combined with the
polymer backing material without using adhesives, rather the
polymer (e.g., TPX) is extruded directly onto the cardstock
material. FIG. 4 shows an extrusion die 230 extruding the hot
molten polymer 240 on the cardstock material coming off of a roll
250. The coated material is cooled down rapidly by a chill roll
260. The material is then delivered on-line to the converting
equipment 270, where it is die cut, sheeted, and packaged.
Alternatively, the coated material can be rolled into roll form and
converted off-line at a later time or in another facility.
[0042] Generally, any polymer is suitable for the polymer layer 134
as long as it has the mechanical properties indicated herein.
Preferred polymers include polymethylpentene, polyolefins (such as
polypropylene, polyethylenes and copolymers of propylene and
ethylene), polyesters, polymethyl methacrylate, polystyrene and
compatible mixtures thereof.
[0043] In a preferred embodiment (FIG. 3), the surface 300 of the
polymer layer is roughened. It may be obtained thereby that the
front side of the top material 130 and the polymer layer 134
applied to the reverse side of the top material have similar haptic
properties, that is, the front and the reverse sides of the
resulting card 120, such as a calling or business card, feel
similar to the touch. Good writeability and a good feeding and
transportation behavior in the printer are also obtained by the
roughening.
[0044] The surface roughness of the reverse side of the polymer
layer 134 is determined by the chill roll 260 after extrusion. (The
chill roll 260 is the roll that cools the melted polymer, as
explained above.) By suitable selection of the chill roll 260, the
surface roughness may be adjusted such that the reverse side of the
polymer layer 134 may be printed with a laser printer (or writing
instrument). A selection of the roughness such that the polymer
layer 134 may be printed by a laser printer (or writing instrument)
represents a further preferred embodiment of the invention.
[0045] In other words, the roughness of the polymer layer 134 is
mainly provided by the structure of the chill roll 260 after
extrusion--the rougher the chill roll, the rougher the polymer
layer. Another method of obtaining a surface roughness is to apply
a coating 300 to the backside of the sheet construction, that is,
to the polymer layer 134.
[0046] The polymer layer 134 of the card sheet 100 according to the
invention is preferably directly applied to the reverse side of the
top material by extrusion, as mentioned above. This allows the
polymer layer 134 to stick to the top material 130 so that no
contact adhesive layer therebetween is required to connect the top
material to the polymer layer.
[0047] In a further embodiment of the invention as shown generally
at 330 in FIG. 5, a second top material 340 may be additionally
applied onto the polymer layer 350, so that the polymer layer is
positioned between two layers of a first top material 360 and a
second top material. In order to produce such a card sheet, the
second top material 360 is also fed from the polymer side when the
polymer sheet is extruded onto the first top material. Also in this
embodiment, the first and the second top materials stick directly
to the polymer layer 350. Both top materials are preferably
provided with punched lines, by means of which the cards may be
broken out from the card sheet 330 by bending them in any
direction. On the other hand, the polymer layer 350 is preferably
not punched. This allows the front side as well as the reverse side
of the card sheet 330 to be printed. Both top materials are as
defined above and may be the same or different from each other.
Additionally, the second top layer may not be extruded, but may
consist of another web of top material. In this manner, the two top
materials may both be paper being held together by TPX. The two
papers in this example do not have to be the same.
[0048] When the carrier material comprises two layers, the bottom
layer 350 can be TPX, the top layer 360 can be white-filled
polyolefin and an optional tie-layer 370 can be provided. Examples
of preferred tie-layer materials include anhydride modified
polymers such as anhydride modified polypropylene, anhydride
modified polyethylene, anhydride modified ethylene vinyl acetate,
anhydride modified ethyl methyl acrylate, anhydride modified ethyl
acrylic acid, and copolymers and mixtures thereof. The polyolefin
can have a suitable topcoat 380. The thickness of the TPX is chosen
to be thin as it tends to be the more costly component; preferably
one to two mil is needed to obtain the snap-break feature of this
invention. The thickness of the top layer 360 depends on the
application, which for business cards would be in the range of
eight to ten mils.
[0049] In a further embodiment as depicted at 386 in FIG. 6, the
polymer layer opposite to the top material is coated with a common
inkjet coating 390 for films, which allows printing with an inkjet
printer. Such inkjet coatings are known to persons skilled in the
art. In most cases, they consist of one or more latex binders
(e.g., vinyl acetate, ethylene vinyl acetate), one or more fixing
agents (e.g., polyamine) and silica.
[0050] The cards 120 broken out of the card sheets 100, etc.
according to the invention may be constructed and used as calling
(business) cards, photograph cards, post cards or the like as would
be apparent to those skilled in the art from this disclosure.
Preferred length and width dimensions are 2.times.3.5 inches for
business cards and 4.times.6, 5.times.7, 2.times.3 and 8.times.10
for photocards. The card sheet itself can, for example, be 8 1/2
.times.11 inches, 8 1/2 .times.14 inches or A4 size.
[0051] The top material 130 can have a.thickness of 150 .mu.m to
250 .mu.m. While the lower limit is important for the breaking
behavior (for very brittle polymers, thinner and, less stiff
materials are acceptable), the upper limit is important for the
desired total thickness of the product.
[0052] Workable thickness ranges for the carrier material 134 are
twenty to fifty g/m.sup.2 or twenty-five to sixty microns. The
lower limit is important for converting. Regarding the higher
limit: thicker polymers can work when semi die cutting the polymer;
thicker polymers can be used when applied by lamination instead of
extrusion; and for a single film construction (such as
polycarbonate) which is semi-punched.
[0053] The mechanism for breaking a card sheet of the present
invention is illustrated in FIGS. 7a, 7b, and 7c. FIG. 7ashows a
cross-section of a portion of a card sheet 100 of the present
invention, preferably after the sheet has been passed through a
printer (or copier) 104 and the desired indicia-printed on the top
surface of the top material 130, which can be paper or cardstock. A
V-shaped die cut 140 is illustrated through the top material and to
the top surface of the (polymeric) carrier material 134. The die
cut 140 is illustrated to have an angle .alpha. wherein .alpha. is
preferably between fifty and eighty degrees, with sixty degrees
being preferred. To separate the individual cards from the rest of
the sheet, the sheet is folded upwards or towards the top material
130 and about the die cut line 140 wherein the folding action is
depicted in FIG. 7bby arrows 400. The bottom layer 134, as can be
understood from FIG. 7c, elongates (as depicted by arrow 410) and
eventually breaks along a clean straight line directly beneath
(adjacent) the die cut line. In other words, with (preferably) only
a single fold it snap breaks cleanly.
[0054] The present card sheet construction. 100 and the
above-described breaking mechanism.can be likened to a hinged door
assembly where the hinge is the film 134 and the facestock 130
(which has been cut through to the film) acts like the door and the
door jamb. Thus, when the "door" is closed, it is overdosed through
the "door jamb." There is a leverage point on the die cut portion
and as the door is forced closed the film 134 stretches and breaks
because of the leverage force. In other words, because the
facestock 130 is fairly thick, when the "door" is closed the film
134 stretches along its back surface and snap-breaks cleanly. Thus,
low elongation of the film is desirable so that it breaks after
stretching only a small amount (and thus the "door" does not fold
or open fully). On the other hand, the tensile strength of the
film. has to be high enough to hold the sheet together so that the
cards do not fall off due to handling stresses including the
stresses exerted on it as it is passed through a printer.
[0055] Another polymer which provides this single fold, clean
snap-break is polyethylene (PE). PE has a tensile strength of eight
to thirty-four MPa, and a minimum elongation at break of ten
percent and a range of ten to 300%. These strength and elongation
values define an alternative definition(s) of the present
invention.
[0056] The ease of breaking towards the paper face 130 is
proportional to 1/.alpha., 1/mod.sub.film, mod.sub.paper,
thickness.sub.paper, 1/thickness.sub.film, and density.sub.papers.
That is, it is, easier to break if the angle of the cut 140 is
narrower (sharper), the modulus (strength or hardness) of the film
is lower, the modulus of the paper is higher, the paper is, thicker
or more dense, or the thickness of the film is lower. These all
assume the die cut is only as far as the film layer. If the die cut
is deeper or shallower, then the depth of the die cut should
replace the thickness of the paper.
[0057] The ease of breaking towards the polymer 134 (in the
opposite folding direction) will be similar to the above "rules"
except that none of the attributes of the paper 130 should play a
role (assuming the paper is completely cut through) and the angle
or sharpness of the die cut will also not play a role. In addition,
because there is no lever point, it is possible that the film 134
will only bend and weaken but not break. If this is the case,
multiple bendings will be needed to cause separation.
[0058] In order for the film layer to break, the strain
(elongation) must be above the elongation at break of the film
layer; in the worst case, when there is a one hundred and eighty
degree bend to break, the elongation is going to be approximately:
elongation parameter =2* (t1+t2)/d wherein t1 is the thickness of
the paper layer, t2 is the thickness of the extrusion coated layer,
and d is the width of the die cut and used as the initial film
length before stretch.
[0059] The invention is explained in detail by the following
examples.
EXAMPLE 1
[0060] Polymethyl pentene (TPX) with a coating weight of twenty
g/m.sup.2 is extruded onto the reverse side of an A4 sheet
consisting of 185 g/m.sup.2 ivory board, which is suited to be
printed with a laser printer and an inkjet printer. The sheet is
punched on the front side in two rows of five calling or business
cards each. The card is broken out by bending it towards the top
material. The mechanical properties of the polymer polymethyl
pentene used are listed in the Table below.
EXAMPLE 2
[0061] TPX with a coating weight of twenty g/m.sup.2 is extruded
onto the reverse side of an A4 sheet consisting of 200 g/m.sup.2
glossy castcoated paper for inkjet photo prints. The reverse side
of the sheet (the side onto which the polymer is extruded) is as
smooth as the front side. The sheet is punched on the front side.
The card is broken out by bending it towards the top material. The
mechanical properties of the polymer polymethyl pentene used are
listed in the Table.
EXAMPLE 3
[0062] TPX with a coating weight of twenty g/m.sup.2 is extruded
onto the reverse side of an A4 sheet consisting of 185 g/m.sup.2
ivory board, which is suitable for laser and inkjet printers. The
sheet is punched on the front side in two rows of five calling or
business cards each. A further coating of the film with an inkjet
coating on the reverse side of the card material allows printing
also on the reverse side, so that a calling card may be
individually produced that may be printed on both sides. The card
is broken out by bending it towards the top material. The
mechanical properties of the polymer polymethyl pentene used are
listed in the Table.
EXAMPLE 4
[0063] A4 sheets consisting of a top material having a weight of
ninety to 125 g/m.sup.2, 30 g/m.sup.2 extruded TPX and a top
material having a weight of ninety to 125 g/m.sup.2, punched on the
front and reverse sides with the same punching tools at the same
location have been produced, with the printing being possible on
the front side and the reverse side and the cards being broken out
by breaking them in any direction. The mechanical properties of the
polymer polymethyl pentene used are listed in the Table.
COMPARATIVE EXAMPLE 1
[0064] The same sheet as in Example 1 above differing in that
polypropylene has been used as the polymer of the polymer layer.
The mechanical properties of the polymer polypropylene used are
listed in the Table.
COMPARATIVE EXAMPLE 2
[0065] The same sheet as in Example 1 differing in that as the
polymer of the polymer layer polyester (filler-free polyethylene
terephthalate) has been used. The mechanical properties of the
polyester used are listed in the Table. TABLE-US-00001 TABLE
MECHANICAL EXAM- PROPERTY OF THE PLES COMPARATIVE COMPARATIVE
POLYMER 1-4 EXAMPLE 1 EXAMPLE 2 Bending stress 23.degree. 90 145
270 [10 MPa] Stress-at-break 16 36 60 [MPa] Elongation at break [%]
50 350 160 Breaking of card sheet Yes No No into separate cards
possible?
FILM-ONLY EMBODIMENTS
[0066] The construction as shown at 430 in FIG. 8 consists of film
only; that is, no paper laminate is used. This construction may be
multi-layer or single layer. It can be produced by conventional.
film-forming means known in the industry and may include extrusion
or coextrusion. The extrusion means may be cast or blown. The
thickness of the construction is dictated by the application and
may range from two mils to fifteen mils. This range is illustrative
only though and may be wider if needed for performance attributes
and/or consumer expectations.
[0067] In a single layer construction, the choice of materials
falls within the range of physical or mechanical performance
characteristics previously outlined. Chemical and physical
characteristics are chosen for properties such as elongation at
break and tensile strength. The layer may consist of a single
polymer, or a polymer blend or alloy, that results in the desired
characteristics. Additives such as fillers or nucleating agents (as
discussed in detail later) may be used to modify the properties in
order to achieve the desired performance.
[0068] In multiple layer constructions, the same set of criteria
should be met; however, only the set of layers 440 that is
contiguous, i.e., not die cut (450), needs to have the desired
physical performance requirements. The non-contiguous layer 460 may
have the desired characteristics, but it is not necessary that it,
have them. Each of the multiple layers can consist of a single
polymer, or a polymer blend or alloy. Fillers, nucleating agents
and other additives may also be used in any or all of the
layers.
[0069] The surface(s) of the film-only construction may be further
modified to accept printing. This modification can consist of
in-process treatments, such as corona treatment, or the addition of
a layer 470 designed to accept printing. Examples include any of a
variety of topcoats well known in the art. And an example of a
preferred topcoat is disclosed in U.S. Pat. No. 5,750,200 (Ogawa,
et al.), and comprises a pigment and a synthetic polymer latex as
the. binder to provide a glossy surface. Topcoats 470 can be
applied by any conventional means such as die coating, spray
coating, etc. The coating should accept the specific printing means
being targeted and have sufficient adhesion to the film to avoid
being easily removed during product use. The coating or
modification can be applied to one or both surfaces (see bottom
coating 480) of the construction 430 depending on the intended use.
Typical weights of coats 470 and 480 range from two g/m.sup.2 to
fifty g/m.sup.2, and more preferably in the range of ten g/m.sup.2
to thirty g/m.sup.2.
[0070] This construction includes die cutting 450 or some other
means of controlling where the product breaks upon bending. The
means of control is sufficient in depth (in the case of die cuts)
or has another characteristic of control such that the construction
cleanly and easily breaks upon bending, but not so easily as to
break prematurely, for example in a printer (104) when being
printed. Control of these properties can be accomplished through
the depth of the die cut, width of the die cut, and so forth.
[0071] Preferred polymers include polymethylpentene, polyolefins
(such as polypropylene, polyethylenes and copolymers of propylene
and ethylene), polyesters, polymethyl methacrylate, polystyrene,
and compatible mixtures thereof. In the case of multiple layers,
the relative thicknesses would depend on costs of the materials and
functionality. For example, one mil of polymethylpentene is
sufficient to enable the snap-break mechanism (see FIGS. 7a-7c);
however, if the ultimate product is a cardstock, additional
materials may be needed to achieve the desired thickness. These
might be chosen from polymers that are relatively inexpensive, such
as commodity-grade polyethylene, but lack the ability to crack
properly. Nine mils of polyethylene can be used to produce a ten
mil construction. In this instance, a tie-layer might be needed to
prevent the layers from separating and can be selected from
materials well known for this purpose. Examples of preferred
tie-layer materials include anhydride modified polymers such as
anhydride modified polypropylene, anhydride modified polyethylene,
anhydride modified ethylene vinyl acetate, anhydride modified ethyl
methyl acrylate, anhydride modified ethyl acrylic acid, and
copolymers and mixtures thereof. Since the polyethylene layer will
likely not provide the snap-break mechanism, die cuts to the
polymethylpentene layer may be required.
[0072] A preferred sheet construction of the present invention
consistently snap breaks. with a single forward bend of forty-five
degrees to one hundred and sixty-five degrees. That is,
back-and-forth or multiple forward bendings are not needed. This
commercially valuable characteristic is not known in the prior art.
Tests were conducted on the following sheets of the present
invention: (1) matte ink jet coated, (2) glossy ink jet coated and
(3) uncoated laser. Each of them broke sixty out of sixty times
with a single forward fold. Accordingly, pursuant to one definition
of the invention the sheet breaks with only a single forward fold
toward the printable top material at least 95% of the time with 95%
confidence, and according to another definition of the invention,
the sheet breaks with only a single forward fold toward the
printable top material at least 93% of the time with 99%
confidence. Important in this "single fold" property is the
matching of the top material (such as paper) with the polymer layer
of the present invention. The. paper is selected to allow the
breaking mechanism to occur.
POLYMER PROCESS EMBODIMENTS
[0073] General concepts common to each of the "polymer process"
alternatives are that the paper is used as one layer, polymer or
film as the second. The thickness of the paper or film depends on
final product requirements. The total construction thickness can
range from two to fifteen mils. Relative thicknesses of the layers
can range from mostly paper with film coating to mostly film with
thin a layer of print-enabling material, such as paper or
topcoating.
[0074] A. Melt Process
[0075] For the melt process a film-forming polymer, or polymer
blend or alloy, is heated to a temperature above its flow point,
conveyed while molten, to a means of contacting a web of paper,
cooled and wound in a roll form. (See FIG. 4 and the corresponding
discussions above.)
[0076] The polymer is chosen as above. Physical properties related
to ease of breaking cleanly are used to select appropriate
polymers. Adhesion to the chosen paper is also used as a criterion
for selecting the polymer. A preferred example utilizes
polymethylpentene (TPX) as the polymeric material. Other polymers
that may also provide suitable properties include polyesters,
polyolefins, polystyrenes, and polymethyl methacrylates.
[0077] The polymer(s) may be melted in a conventional melting
apparatus including single screw extruders such as those
manufactured by Davis-Standard, twin-screw extruders such as those
manufactured by Leistritz, or heated pots or melters (Nordson as an
example). The exact temperature will depend on the materials'
temperature stability and viscosity. Typical extruder conditions
will depend on the materials but might include temperature ranges,
of 250.degree. F. to 650.degree. F. The molten polymer(s) are
conveyed to a die by means of the extruder, a gear pump or any
other suitable means. The die causes a sheet of molten polymer(s)
to be formed, and this sheet is then deposited onto a paper or
other substrate. The die may be in contact, or nearly so, with the
substrate as in typical slot coating operations. Alternatively, the
die may be located a distance from the substrate as in typical
extrusion coating operations. Additionally, a nip point may be
employed to ensure good contact of the film and substrate.
[0078] The polymer(s) may be further modified as above using
fillers, nucleating agents, etc. (as described elsewhere in this
disclosure in greater detail) and still remain within the scope of
the invention.
[0079] The paper chosen should provide additional properties that
are required for the application. The paper may need to be die cut,
textured, printed upon, erased and so forth. It may also need to be
thick enough to provide the overall thickness required for the
application. Treatment of the paper may be required for adhesion or
print receptivity. Means of adhesion promotion may include a
primer, adhesives or corona treatment. Means of improving ink
receptivity may include topcoats (mentioned above) or additives to
the paper.
[0080] In addition to printing on the paper side of the laminate,
the film side might also be printed upon. The choice of film may
allow this, or, the film side may be treated with a means of
enhancing printability. As above, these may include corona
treatment or topcoats.
[0081] As an example, an extruder with a 21/2 inch diameter screw
was used to extrude a 35 MFI Basell PD-702 polypropylene
homopolymer resin through a twelve inch die, with melt temperatures
between 550.degree. F. and 600.degree. F. The melt was coated
directly onto paper with paper thickness at 8.6 mil and the
polypropylene layer thickness at one mil. The line speed for
winding was at fifty ft/min.
[0082] B. Solution Process
[0083] The "solution process" concept involves dissolving a
suitable material or blend of materials in an appropriate solvent,
coating the solution onto the paper, then driving the solvent off.
Conventional solvent coating means can be used. Generally, ovens
operating at temperatures that depend on the choice of solvent are
used in-line with the coating process in order to achieve a
uniform, dry film. Fillers might also be useful.
[0084] An example of suitable coating materials are aqueous acrylic
coatings produced by Rohm & Haas and sold under the trade name
RHOPLEX, containing about 40% to 60% solids, applied by any means
capable of metering the desired coat weight onto the desired
substrate. The coating is subsequently dried at oven temperatures
of about 150.degree. C. to 160.degree. C. to obtain 100% solids
acrylic coating.
[0085] C. Pre-Polymer Process
[0086] The "pre-polymer process" uses pre-polymers, monomers and
optionally (if needed) initiators and accelerators. A mixture of
these are coated onto the paper substrate, such as by conventional
means including slot die coating, knife coating or gravure, to a
uniform thickness. The mixture may, be heated to aid coating, but
heating may not be needed if the viscosity of the mixture is low.
The pre-polymer mixture is, then subjected to curing conditions to
form the final film. The final film should have sufficient physical
properties to enable the snap-break mechanism. Die cutting, surface
treatments, etc. would then be performed to form the final
product.
[0087] Various materials can be used to produce films, including
acrylates, methacrylates, and multifunctional acrylates and
methacrylates. These materials may be available from Sartomer
Corporation. A suitable blend of these materials can be fashioned
such that the final cured polymer has the desired snap-break
characteristics. The blend can be coated onto suitable paper, and
can be cured in a number of ways.
[0088] Thin (generally one mil or less) films can be produced by
the addition of a photoinitiator such as benzophenone; other
photoinitiators known in the industry including those falling
within classes of phenones, and azo or diazo compounds can be used.
The amount of photoinitiator will impact the final properties, and
can be determined experimentally. After coating, the pre-polymer is
irradiated with UV light (high-pressure mercury lamps are generally
used), whereupon polymerization occurs, resulting in the final
film.
[0089] Either thermal or electron beam methods may be used instead
of UV light. These methods in particular can be used for thicker
films where UV light will not penetrate deep enough to effect cure
throughout the film. In the case of thermal curing, a thermal
initiator will be added instead of a photoinitiator Thermal
initiators generally will be organic peroxides or diazo compounds.
DuPont makes a class of initiators sold under the trademark VAZO,
which can be used. The choice of initiator depends on the
difference between the temperature required for coating and the
temperature required for curing. An initiator is chosen that does
not cause polymerization to occur prematurely at coating
temperatures. The amount of initiator will impact the final
properties of the film and. can to be determined experimentally.
The temperature required for cure depends on the initiator chosen
and the speed of the desired reaction, and can also be determined
experimentally.
[0090] In the case of electron beam curing, no initiator is needed,
since the electron beam will produce free radicals upon impingement
with the pre-polymer. Doses of radiation required can range from
ten to fifty kilograys (one to five megarads).
[0091] Another pre-polymer that may be useful would make use of
organic epoxides. Suitable epoxy mixtures include organic epoxides,
accelerating agents (such as nonyl phenol) and initiators. Many
initiators for these systems exist and can include metallic esters
(such as organic titanates), free-radical initiators and cationic
initiators. Many of these systems, however, consist of two parts
and need to be blended just prior to curing. Control of the cure
rate can be done through careful choice of materials. Most epoxy
materials are hard and brittle and may be suitable as a crack layer
as long as they have enough flexibility to survive use in desktop
printers. Flexibilized bisphenol A epoxy acrylates such as those
produced by UCB Chemicals (Belgium) and sold under the trademark
EBECRYL are preferred flexible epoxy materials.
POST-PROCESSING EMBODIMENTS
[0092] Any of the previously mentioned constructions may be used
for this example. Thicknesses of the relative layers can be
adjusted to-the desired physical responses being sought in terms of
overall thickness, cost of construction, printability, and so
forth. The construction may be assembled by any of the means
discussed.
[0093] A. Heat Treatment (Aging)
[0094] ln general, a sample is heat aged at elevated temperatures
to encourage crystallization within the polymer layer. More
crystallization will likely improve the snap-cracking effect since
polymeric crystals are more brittle than amorphous polymers. The
temperature used should be above the T.sub.g of the polymer, but
below the melt or flow temperature. This will allow rearrangement
of the polymer molecules into lower energy states (crystallized).
The treatment may be conducted while the product is unconverted, in
roll form or after converting and/or packaging.
[0095] "A polymer solid is partially crystalline, such as
polyethylene and poly(ethyleneterephthalate), or non crystalline,
such as commercial poly(methylmethacrylate) and polystyrene.
Partially crystalline polymers, called crystalline polymers, are
constructed by a complicated aggregation of crystalline and
amorphous regions. In the amorphous region the molecular chains are
in a conformationally random state. In the crystalline region,
polymer chains are extended in a definite characteristic structure
and packed together regularly, forming a crystallite. . . .
Crystallization of polymers with low crystallinity is accelerated
by heat treatment under suitable conditions. The weight fraction of
the crystalline regions determines the degree of crystallinity."
Encyclopedia of Polymer Science and Technology--Supplement Volume
pp. 187. "Crystalline polymers are not-fully ordered, but are
partially crystalline (semi-crystalline), typically less then about
80%. . . . Techniques employed to access relative and absolute
degrees of crystallinity . . . five widely used methods . . . X-ray
Diffraction, Volumetric, Thermal, Infra-red and Raman spectroscopy,
and NMR." Vol. 4, pp. 482.
[0096] As an example, polypropylene may be used as the snap layer.
The T.sub.g of polypropylene is close to 0.degree. C. and its
melting temperature is 162.degree. C. The construction consisting
of about one mil of polypropylene. extrusion coated onto cardstock
(8.6 mils) was heat aged for two days at 200.degree. F. Possible
semi-crystalline polymers subject to this treatment include
semi-crystalline polymers such as polypropylene, HDPE, LLDPE, PET,
and PETG.
[0097] As another example with polypropylene used as the snap
layer, the construction, consisted of about one mil of
polypropylene extrusion coated onto cardstock (8.6 mils) was heat
aged for seventy-two hours at 75.degree. F. to 120.degree. F. and
50% relative humidity. Possible semi-crystalline polymers subject
to this treatment include polypropylene, HDPE, LLDPE , PET, PETG
and polystyrene.
[0098] The length of time under the condition may vary, but will be
a tradeoff between the cost of warehousing in heated buildings and
the rate of crystallization. However, it is common practice in the
industry to store films such as PET and PP (cast or oriented) under
ambient conditions, such as in a warehouse for seventy-two hours,
before making them available for further converting of end-use
application.
[0099] B. Actinic Radiation
[0100] In general, the roll form of the product is treated with
ionizing radiation either inline with assembly of the construction
or in a separate step.
[0101] It is known that polymeric materials subjected to radiation
energy can generate free-radicals and under an oxygen environment
can subsequently oxidize the polymer. The effect may continue over
weeks or months as the free radicals generated in the system
continue to migrate and react. Materials such as
polytetrafluoroethylene and polypropylene can easily lose 50% of
their original elongation at break property when they were
irradiated at or below one hundred kilograys (kGys). Such a loss of
elongation properties can make the coated material easier to break
off.
[0102] In the case of high-energy radiation (electron beam, gamma,
x-ray, etc.) either side of the construction may be irradiated,
since the radiation has sufficient energy to penetrate the entire
thickness. However, the preferred side of irradiation is the film
side, since the radiant energy diminishes with depth. Preferred
doses for electron beam radiation range from ten to two hundred
kilograys (one to twenty megarads) at very high dose rates (greater
than ten kilograys per hour). Lower radiation doses (under ten
kilograys for polypropylene ) can be used if they are processed at
slower dose rates such as five to fifty grays per hour.
[0103] Alternative preferred doses for electron beam range from ten
to fifty kilograys (one to five megarads). There may also be a
so-called dose-rate effect. The dose-rate effect is the difference
in properties that occurs when a given dose is delivered over a
varying amount of time. For example, two samples may both receive
thirty kilograys of radiation, but one receives it while running at
one hundred fpm while the other runs at five hundred fpm. If the
properties of interest differ between these two samples, then there
is a dose-rate effect.
[0104] As an example of this alternative, a roll of
paper/polypropylene construction was made by extrusion coating of
one mil layer thickness of polypropylene on to 8.6 mil paper. The
finished roll was sent for electron beam irradiation at one hundred
kilograys (kGy) to reduce its elongation at break by more than 50%,
at a dose rate of more than ten kGy/hour. It is expected to yield a
coated paper which is easy to die cut and break along the
edges.
CONVERTING EMBODIMENTS
[0105] A primary idea behind the "converting" embodiment is to show
that the snappable film can be scored or partially cut to enhance
the feature. It should be clear from the film-only embodiment that
partially cutting through the film should work. As an alternative
to cutting only to the film backing (as described earlier in this
disclosure) the cutting can be somewhat deeper. For example cutting
only one-quarter of the way through the backing layer above may be
preferred. A suitable range may be between 0% (not cut) and
90%.
[0106] Other converting embodiments include the die being shaped
differently. Examples are two-side sharpening resulting in a
knife-like point and one-side sharpening resulting in a razor-like
point.
[0107] The die geometry can affect the performance considerably. If
the cut is V-shaped, some degree of bending is needed before the
stretching. process starts in the polymer. In addition, if the "V"
is wide, the polymer may not be stretched enough to cause the
fracture. A narrow cut in the paper can reduce the degree of
bending required to generate the fracture in the polymeric layer.
The extent of the cut into the polymer can have positive and
negative effects. If the cut extends into the polymeric layer, it
helps the polymer to fracture upon bending by reducing the
thickness and introducing a fracture initiating point. However, it
may deteriorate the mechanical properties of the product,
especially when it is passing over the rollers and being
printed.
[0108] The adhesion between the polymeric layer and the paper has
to be strong enough in order to concentrate the stress on the
fracture point. The structure and the rigidity of the paper
substrate and its thickness are also important factors. If its
compression strength is low, the paper is compressed at the cut as
the result of bending instead of stretching the polymer.
ADDITIVES EMBODIMENTS
[0109] Various nucleating agents and pigments can be incorporated
into the film formulations of the present invention. The amount of
nucleating agent added should be an amount sufficient to provide
the desired modification of the crystal structure while not having
an adverse effect on the desired properties. It is generally
desired to utilize a nucleating agent to modify the crystal
structure and provide a large number of considerably smaller
crystals or spherulites to improve the stiffness, and the
die-cuttability of the film. Nucleating agents which have been used
previously for polymer films include mineral nucleating agents and
organic nucleating agents. Examples of mineral nucleating agents
include carbon black, silica, kaolin and talc. Among the organic
nucleating agents which have been suggested as useful. in
polyolefin films include salts of aliphatic mono-basic or di-basic
acids or arylalkyl acids such as sodium succinate, sodium
glutarate, sodium corporate, sodium 4-methylacrylate, aluminum
phenyl acetate, and sodium cinnamate. Alkali metal, and aluminum
salts of aromatic and alicyclic carboxylic acids such as aluminum
benzoate, sodium or potassium benzoate, sodium beta-naphtholate,
lithium benzoate and aluminum tertiary-butyl benzoate also are
useful organic nucleating agents. Substituted sorbitol derivatives
such as bis (benzylidene) and bis (alkylbenzilidine) sorbitols
wherein the alkyl groups contain from about four to about eighteen
carbon atoms are useful nucleating agents. More particularly,
sorbitol derivatives such as 1,3,2,4-dibehzylidene sorbitol,
1,3,2,4-di-para-methylbenzylidene sorbitol, and
1,3,2,4-di-para-methylbenzylidene sorbitol are effective nucleating
agents for polypropylenes. Useful nucleating agents are
commercially available from a number of sources. Millad 3988 and
Millad 3905 are sorbitol nucleating agents available from Milliken
Chemical Co.
[0110] The amounts of nucleating agent incorporated into the film
formulations of the present invention are generally quite small and
range from about one hundred to about 2000 or 4000 ppm of the
film-forming layer. Preferably the amount of nucleating agent
should not exceed about 2000 ppm, and in one embodiment, a
concentration of about three hundred to five hundred ppm appears
optimum.
[0111] Similar nucleating agents can be used for other
semi-crystalline polymers that crystallize slowly as well. Ranges
of concentrations are listed in the paragraph above for the
additives as well. The amount of material added will be a tradeoff
between rapid crystallization and poor performance (too much
additive is used) and slow crystallization and good performance
(too little additive used).
[0112] Nucleating agents such as the dibenzylidene sorbitol-based
Millad 3905 or Millad 3988 were used in polypropylene to reduce the
spherule size and thus to improve the clarity of the polypropylene.
Other sorbitol-based nucleating agents include IRGACLEAR sold by
Ciba Specialty Chemicals and NC-4 from Mitsui Toatsu Chemicals in
Japan. These nucleating agents are also called clarifiers. Other
nucleating agents can be used including phosphate esters based
NA-11 and NA-21 supplied by Asahi-Denka Kogyo of Japan, a
norbornane carboxylic acid salt based HPN-68 by Milliken Chemical
Company.
[0113] Basell PD-702 and PD-702N material can be used for extrusion
coating on paper for comparison purposes. PD-702N is the nucleated
version of the same PD-702 homopolymer PP resin, with 2000-2500 ppm
quantity of sorbitol-based nucleating agent added in the material
formulation. It is believed the nucleating agent will change the
physical property of the polypropylene surface layer and reduce its
elongation at break, such that the paper will be quick and easy to
snap-break. Both polypropylene materials, at one mil thickness, can
be extrusion coated on to 8.6 mil paper.
[0114] Significant reduction of material's elongation at break can
be achieved by adding fillers into the material formulation. In
this particular example fifteen pph of three micron Camel-WITE
calcium carbonate (Genstar Stone Products Company) was compounded
with Basell PD-702 polypropylene resin, and extrusion coated at one
mil thickness on to the 8.6 mil paper.
[0115] The additives approach is suitable for any of the
constructions listed, whether film-only or film/paper-based.
Additional Alternative Constructions
[0116] Any of these approaches may be combined with others. For
example, a construction that has nucleating agents added can be
heat treated. The effect may not be linearly additive, but may
provide incremental improvements in properties.
[0117] As may be understood from the above discussions, the
mechanical properties of the polymer layer are important to
snap-break out individual cards (or sheet portions) with smooth
cutting edges from the card sheets.
[0118] One preferred use or construction of generally any of the
above card sheet embodiments is printed business cards. Another is
photo cards 500 (FIG. 9). which would have a photoreceptive surface
510 for receiving a photo image or photoprinting 520. Examples of
photoreceptive coated papers which. can be used for the photo card
sheets are those manufactured by Oji Paper Co., Ltd. (Tokyo,
Japan), Mitsubishi Paper Mills Limited (Tokyo), Japan Pulp and
Paper Company Limited (Tokyo), Zanders USA (Wayne, N.J.), and Sihl
Paper Company (Switzerland). These are cast coated glossy papers,
instant dry papers, photo quality papers and photorealistic papers.
The coatings are swellable or microporous coatings.
[0119] A further alternative to all of the constructions disclosed
in this disclosure is to apply a backcoating 530 to the polymer
layer. The backcoating can be used to reduce static electricity,
improve writability, and/or improve print quality in laser printers
(because static electricity disturbs toner transfer). The
backcoating can be a standard antistatic coating used by
manufacturers of filmic products, modified for good anchorage to
the polymer as would be apparent to those skilled in the art from
this disclosure.
[0120] Additionally, while the printing is preferably inkjet or
laser means, other methods include gravure, offset printing, and
other press-type printing techniques. (Hand) writing is another
method, and the rationale for it is that users may wish to quickly
convey additional information informally, as needed, for example,
personal telephone numbers on the backs of business cards. Printing
press techniques can be used to standardize portions of the
separable (sheet) members, while allowing personalization in other
areas. A business card example of this technique is that a company
has its logo printed on business card sheets. At a separate time,
an employee can (hand)print his particular (individual) information
on the card. Topcoats, corona treatment and other means by which
the materials can be made inkjet and/or laser receptive can also be
used to make the surface(s) receptive to other marking means (pen,
pencil, etc.) as would be apparent to those skilled in the art from
this disclosure.
[0121] Although preferred embodiments are for traditional cards,
the present invention is not so limited. It can be a thin sheet, as
thin as four mils. The absence of a central flexible adhesive layer
allows for such thin gauges. Rather, it can include other
embodiments/uses (for parts of sheets) such as inserts on hanging
file folders, which tend to be as thin as paper and are perfed to
be torn apart. The present invention can offer cleaner inserts.
Other applications include CD jewel case inserts.
Method for Analysis of Optical Roughness of the Fracture
Interface
[0122] 1. Introduction
[0123] Generally, the above-described products are composite
structures made of a polymeric layer coated on different types of
high quality paper products such as business cards and photo
quality papers. The product is easily fractured and separated by
the customers after printing the desired information or photographs
using inkjet or laser printers. One of the main advantage of the
product over other existing perforated papers products is the
smoothness of the interface after the fracture. The smoothness of
the fracture interface can be described as a combination of the
optical (visual) as well as mechanical (touch) smoothness.
[0124] A method of-the present invention to quantify the optical
smoothness in these products will now be described. This method is
based on the optical microscopy-of the fracture interface and
further processing of the image and calculation. The interface
roughness values can be used as one measure (among others) to
compare the optical smoothness of the fractured products.
[0125] 2. Sample Preparation and Image Capture
[0126] Samples are prepared by bending and fracturing the product
towards the paper substrate. The fractured samples are handled
carefully without touching the fracture interface. This ensures
that the roughness will not change before capturing the image under
the optical microscope.
[0127] The samples are placed over a dark background and the
interface image is digitally captured using the Keyence optical
microscope in reflection mode. FIG. 10 represents the digital image
of a sample prepared using this method. It is a digital image of
the fracture interface (.times.25) in a product. The insets in that
figure show the higher magnification (.times.175) images of the
interface. For a given sample, several digital images are captured
from different locations on the product in order to collect enough
data for further processing and calculations.
[0128] 3. Image Processing and Calculations
[0129] An image processing technique is used to extract the
interface contours from the captured digital images. The captured
images need initial enhancements before further contour extraction.
FIG. 11 shows the enhancement process for a small region of the
digital image.
[0130] The image conditioning and enhancement process is: (a)
original image, (b) binary image, and (c) de-speckled image.
[0131] In the-first step, the brightness and contrast of the
original image is enhanced and then it is converted to binary (0's
and 1's ) as shown in FIG. 11(b). The speckles in the dark region
are simply removed by a morphological opening process (See FIG.
11(c)). See J. C. Russ, "The Image Processing Handbook", CRC Press,
Boca Raton (1992). This de-speckled image is now ready for the
contour extraction.
[0132] The fracture interface contour at this point is represented
by the interface between the white and dark regions. This interface
is easily extracted by further morphological processing of the
image in FIG. 11(c). Assume a symbol A represents the image in FIG.
11(c). This image is subjected to the erosion process (see J. C.
Russ, "The Image Processing Handbook", CRC Press, Boca Raton
(1992)), which is then called image B. The erosion process simply
removes a single layer from the white regions of the image that
have common interface with the dark regions. The eroded image B is
shown in FIG. 12. Now, the only difference between the image A and
B is the fracture interface, which is absent in B.
[0133] The interface image is extracted by subtracting the image B
from A as shown in FIG. 13(a) (image C). Inverting image C
generates the fracture interface image D.
[0134] The fracture interface in image D is converted to a profile
h(x) by a raster-to vector algorithm. This profile is then
corrected for any linear trend and called g(x). The roughness value
for this profile is then calculated from: rms =square root of
(g(x)-<g>).sup.2 where rms is the root mean square (which is
a measure of the interface roughness), and <.> is a simple
average over the whole data set.
[0135] 4. Examples
[0136] As an example, three different pictures are captured from
the fracture interface of a product of this disclosure. FIG. 14
shows the original pictures taken by the optical microscope. Using
the algorithm set forth above, the fracture interface roughness is
calculated.
[0137] FIG. 15 represents the fracture interface contour extracted
from the digital images. The rms values for these three interfaces
are also given in this figure. The straight lines in this graph are
the linear trends in the data, which is used for corrections and
obtaining the profile g(x). The interface roughness values for this
particular product is 61.31.+-.6 microns, which is calculated by
averaging these three values.
[0138] 5. Test Results
[0139] Using the roughness analysis method described above, tests
were conducted. on various prior art paper constructions and
various constructions of the Invention and the following average
rms and (rms standard deviation) measurements were determined:
Avery Maxell CR-2SA4LX4-glossy-long cut direction--32.4-(9.1);
Avery Maxell CR-2SA4LX4-glossy-short cut direction--24.4 (7.7);
Avery InkJet microperfed business cards--73.4 (9.6); Invention
matte-lnkJet coated (IJC)-long cut--29.3 (6.7); Invention matte
IJC-short cut--23.1 (8.5); Invention glossy IJC-long cut--20.5
(3.3); Invention glossy IJC-short cut--19.9 (5.5); Invention
uncoated laser-long cut--10.9 (2.2); and Invention uncoated
laser-short-cut--2.6 (0.7). All samples were folded toward the
printable face first, then folded back and forth as necessary to
break. The cut directions on the sheet are indicated above. And the
"Avery Maxell" is existing photosheet paper with die cuts. As can
be seen the Invention resulted in significantly smoother edges.
6. CONCLUSIONS
[0140] Thus, a new method is set forth above in order to quantify
the interface optical roughness of the product. This method is
based on optical microscopy and further image processing and
calculations. The interface roughness is reported as a single value
(rms). These data can be Used for the comparison as well as
checking the quality of the product. However, since this method is
based on optical processing of the samples, the optical roughness
values do not include the smoothness-to-touch of the fracture
interface. To include the hardness and sharpness of the interface,
this method needs to be further developed and perhaps to
be-combined with other test methods.
[0141] Thus, from the foregoing detailed description, it will be
evident that there are a number of changes, adaptations and
modifications of the present invention that come within the
province of those skilled in the art. The scope of the invention
includes any combination of the elements from the different
species, embodiments, functions and/or subassemblies disclosed
herein, as would be within the skill of the art. It is intended
that all such variations not departing from the spirit of the
inventions be considered as within the scope thereof.
* * * * *